1 /*
   2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 #ifndef SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP
  25 #define SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP
  26 
  27 #include "logging/logLevel.hpp"
  28 #include "memory/allocation.hpp"
  29 #include "runtime/atomic.hpp"
  30 #include "utilities/globalDefinitions.hpp"
  31 
  32 class LogOutput;
  33 
  34 // Data structure to keep track of log outputs for a given tagset.
  35 // Essentially a sorted linked list going from error level outputs
  36 // to outputs of finer levels. Keeps an index from each level to
  37 // the first node in the list for the corresponding level.
  38 // This allows a log message on, for example, info level to jump
  39 // straight into the list where the first info level output can
  40 // be found. The log message will then be printed on that output,
  41 // as well as all outputs in nodes that follow in the list (which
  42 // can be additional info level outputs and/or debug and trace outputs).
  43 //
  44 // Each instance keeps track of the number of current readers of the list.
  45 // To remove a node from the list the node must first be unlinked,
  46 // and the memory for that node can be freed whenever the removing
  47 // thread observes an active reader count of 0 (after unlinking it).
  48 class LogOutputList VALUE_OBJ_CLASS_SPEC {
  49  private:
  50   struct LogOutputNode : public CHeapObj<mtLogging> {
  51     LogOutput*      _value;
  52     LogOutputNode*  _next;
  53     LogLevelType    _level;
  54   };
  55 
  56   LogOutputNode*  _level_start[LogLevel::Count];
  57   volatile jint   _active_readers;
  58 
  59   LogOutputNode* find(LogOutput* output);
  60   void remove_output(LogOutputNode* node);
  61   void add_output(LogOutput* output, LogLevelType level);
  62   void update_output_level(LogOutputNode* node, LogLevelType level);
  63 
  64  public:
  65   LogOutputList() : _active_readers(0) {
  66     for (size_t i = 0; i < LogLevel::Count; i++) {
  67       _level_start[i] = NULL;
  68     }
  69   }
  70 
  71   // Test if the outputlist has an output for the given level.
  72   bool is_level(LogLevelType level) {
  73     return _level_start[level] != NULL;
  74   }
  75 
  76   // Set (add/update/remove) the output to the specified level.
  77   void set_output_level(LogOutput* output, LogLevelType level);
  78 
  79   // Bookkeeping functions to keep track of number of active readers/iterators for the list.
  80   jint increase_readers();
  81   jint decrease_readers();
  82   void wait_until_no_readers() const;
  83 
  84   class Iterator VALUE_OBJ_CLASS_SPEC {
  85     friend class LogOutputList;
  86    private:
  87     LogOutputNode*  _current;
  88     LogOutputList*  _list;
  89     Iterator(LogOutputList* list, LogOutputNode* start) : _current(start), _list(list) {
  90     }
  91 
  92    public:
  93     ~Iterator() {
  94       _list->decrease_readers();
  95     }
  96 
  97     LogOutput* operator*() {
  98       return _current->_value;
  99     }
 100 
 101     void operator++(int) {
 102       _current = _current->_next;
 103     }
 104 
 105     bool operator!=(const LogOutputNode *ref) const {
 106       return _current != ref;
 107     }
 108   };
 109 
 110   Iterator iterator(LogLevelType level = LogLevel::Last) {
 111     increase_readers();
 112     return Iterator(this, _level_start[level]);
 113   }
 114 
 115   LogOutputNode* end() const {
 116     return NULL;
 117   }
 118 };
 119 
 120 #endif // SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP